- 216. By Oleg Tsarev on 2012-02-19
- 215. By Oleg Tsarev on 2012-02-15
- 214. By Oleg Tsarev on 2012-02-15
- 211. By Oleg Tsarev on 2012-02-07
- 209. By Oleg Tsarev on 2012-02-05
- 208. By Oleg Tsarev on 2012-01-16
Return back Percona's "innodb_
stats_method= nulls_ignored" algorithm.
I added new value "nulls_
ignored_ exact" for variable innodb_ stats_method.
Current upsteam "nulls_ignored" algorithm calculate not_null values on every estimated (random) page, and after that try to approximates total value count.
Unfortunately, this algorithm works incorrectly on mostly null indexes (see MySQL Bug #63320).
Percona'a algorithm excludes from estimation pages with nulls, calculates the count of different values and approximates total value count.
This algorithm works correctly on mostly null indexes, but has limitation - it works correctly just on one-column-key indexes. On compound-keys algorithm can works incorrectly (I didn't test this).
Unfortunately, I can't imagine now how to discard this limitation.
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